Method of working and heat treating aluminum-magnesium alloys and product thereof



United States Patent" METHOD OF WORKING AND HEAT TREATING ALUMINUM MAGNESIUM ALLOYS AND PROD- UCT THEREOF Hugh S. Cooper, Shaker Heights, Ohio, assignor to William F. Jobbins, Incorporated, Aurora, Ill., a corporation of Illinois No Drawing. Application October 12, 1956 Serial No. 615,456

3 Claims. (Cl. 148--11.5)

This invention relates to aluminum alloys in which magnesium is a major alloying element and it relates more particularly to the provision of aluminum-magnesium alloys which are wrought alloys, having been fabricated by forging, rolling, extruding and other fabricating procedures involving substantial mechanical working.

Wrought alloys which are known as heat-treatable alloys comprise those in which solid solutionand precipitation heat treatments produce the desired tempers in the final product, while non-heat treatable wrought alloys comprise those where the various tempers are produced by strain hardening or the like, solution heat treatment having no significant effect. While the former have generally highest strengths, they arev characterized by low corrosion resistance, particularly in the case of aluminum-magnesium heat-treatable alloys (this low resistance apparently involves predominantly the phenomenon known as stress corrosion). Theseheat-treatable alloys must therefore be protected by cladding in many if not most applications.

The present invention discloses how to produce wrought alloys which inherently have high corrosion resistance and do not require cladding but which have strength properties closely approaching those of the best of the heat-treatable wrought alloys of the priorart. The strength properties of the wrought alloys provided according to the present invention and the heat-treatable alloys now in use are even more comparable when the latter are taken as clad alloys, which indeed must be done for a fair comparison in the cases of the many specific uses where corrosion resistance is required. Of course, it follows that the strength properties of alloys provided according to the present invention far exceed those of the commercially useful, non-heat-treatable wrought aluminum alloys of the prior art.

I have discovered that certain aluminum-magnesium compositions, heretofore regarded as casting compositions, will respond under certain conditions to the common mechanical workingprocesses to be converted to wrought alloys having the advantages mentioned above. These alloys comprise what may apparently be most appropriately characterized as non-heat-treatable alloys which may be employed either in the cold worked or annealed state. The surface finishes of these alloys are of exceptionally high quality and they are therefore much superior in this respect even to present commercially useful, nonheat-treatable wrought alloys.

Accordingly, an object of the invention is to provide wrought aluminum alloys which have strength properties comparable with the best heat-treatable wrought aluminum alloys of the prior art, but which do not require cladding for use in numerous applications where such prior art heat-treatable wrought aluminum alloys would require cladding.

Another object of the invention is to provide wrought aluminum alloys which are superior to all others in many applications in the manufacture of architectural structural components, marineequipment, cooking utensils, dairy equipment and otheruses.

As anernbodiment of the invention (which is given by way of example and not by way of limitation to all the precise details thereof) an alloy is provided from those alloys comprising magnesium 5-8%, titanium .10-.25%, manganese .l0-.25%, beryllium .0005-.05%, balance, aluminum; or from alloys comprising the same components plus .001-.05% boron, this element appearing to be of benefit in most instances. Other metals which may be present may include copper, iron, silicon and the like, and they can be considered impurities. Impurities should not exceed a combined total of about 50% of the alloy.

Certain alloys included within the ranges specified above have gained Wide acceptance throughout the aluminum industry and are presently commonly known as Almag 35. They are, however, used only in the cast condition as produced in sand or permanent molds or the like. In this connection, reference is made to U. S. Patents 2,564,044; 2,583,473 and 2,733,991. These Almag 35 alloyshave not been found useful for the manufacture of wrought aluminum alloy products.

The. alloy providedfrom those specified above is soaked for a period of hours. at a temperature of from about 700-750 F. The minimum soaking time may vary from hour. to hours. or more, preferably not over 24hours in most cases, depending on the massiveness of the metal. If any doubt exists as to sufficiency of the soaking of a given kind and shape of charge, the soaking time maybe made excessive and may then be varied downwardly in succeeding trials with similar chargesuntil. a workable minimum is established.

After soaking, the charge is formed by operations which involve mechanical working such as forging, rolling, extruding, and the like, until the charge is reduced in cross-sectional area about and preferably at least within the range of about from 40 to During this initial reduction, the metal ismaintained at temperatures not exceeding, and not substantially below, the previously mentioned range of from about 700750 F. This may be done, for example, by frequent passes through or into and out of a furnace pit or other hot zone. After this initial reduction, the metal is fully anneal d by repeating the soaking step at the previously mentioned range of from about 705F750" F.

An aluminum-magnesium alloy provided in this manner may be regarded at this stage as a processed raw material which may be further reduced at later times (and after shipment, if desired). by cold working during conventional forming operations at least down to 16% of starting cross section. It can be thereafter annealed, if desired.

An aluminum-magnesium product made according to the above disclosure was found to have an ultimate strength of 75,000 pounds per square inch,v a yield strength of 60,000 pounds per square inch, and an elongation of about 5%. After full annealing, the same material was found to have an ultimate strength of 50,000 pounds per square inch, a yield strength of 26,000 pouudsper square inch, and an elongation of 32%.

For comparison purposes, these results areset forth in the following tablestogether with' several of the wellpresently known heat-treatable wrought aluminum alloys.

known wrought aluminum alloys of both the heat-treatable and non-heat-treatable types:

Comparison table-Nt annealed Material- Ult. Yield Alcoa Strength, Strength, Elong., Alloy p. s. i. p. s. i. percent Desig.

Present Product, Work-l1ardened non 9 75,000 60, 000 5 Non-heat-treatable-Oold worked stalndairrd solifition lllgal, treated and 6i, i2, aum um enco wore. 6,

" i as: as a ien ar 1 01a y age 1 Heat treatable" solution heat treated and 14S unknown unknown Not as an ass a then artificially aged. 75S 82, 000 72, 000 17 Comparison tabla-Annealed Material- Ult. Yield Alcoa Strength, Strength, Elong, Alloy p. s. i. p. s. i. Percent Desig.

Present Product, Fully annealed none 50, 000 26, 000 32 N on-heat-treatable 2; $3 Standard aluminum I its 251 000 i0, 000 21 alloys. Clad (Alelad).. 1 248 26,000 11,000 19 Heat treatable..-. fg fi gzfi Not Clad i are 27: 000 11,000 19 758 33, 000 15, 000 17 It is believed apparent that specific details of the practice of the invention may be varied without essential departure from the teachings thereof. All such variations are contemplated as may be covered by the following claims, either literally or under the doctrine of equivalents.

What is claimed is:

1. A method for making a wrought aluminum alloy material comprising soaking a body of metal comprising magnesium 5 to 8%, titanium .10 to .25%, manganese .10 to .25%, beryllium .0005 to .05 impurities not more than .50%, balance aluminum, for a period of from minutes to 40 hours at a temperature of about from 700 to 750 F., reducing said body by forming to about from 40 to 60% of starting cross-section while maintaining said body within a temperature range not greater than and not substantially below about from 700 to 750 F. and then further soaking the body at about from 700 to 750 F. to fully anneal it whereby the resulting alloy material is greatly further reducible by cold working and is capable of achieving thereby strengths comparable with those of presently known heat-treatable wrought aluminum alloys while also having corrosion resistance far superior to that of presently known heat-treatable wrought aluminum alloys.

2. A method for making a wrought aluminum alloy material comprising soaking a body of metal comprising magnesium 5 to 8%, titanium .10 to manganese .10 to .25 boron .001 to .05 beryllium .0005 to .05%, impurities not more than .50%, balance aluminum, for a period of from 15 minutes to hours at a temperature of about from 700 to 750 F., reducing said body by forming to about from 40 to 60% of starting cross-section while maintaining said body within a temperature range not greater than and not substantially below about from 700 to 750 F. and then further soaking the body at about from 700 to 750 F. to fully anneal it whereby the resulting alloy material is greatly further reducible by cold working and is capable of achieving thereby strengths comparable with those of presently known heat-treatable wrought aluminum alloys while also having corrosion resistance far superior to that of 0 ing magnesium 5 to 8%, titanium .10 to 25%, manganese .10 to .25%, beryllium .0005 to .05 impurities not more than .50%, balance aluminum, for a period of from 15 minutes to 40 hours at a temperature of about from 700 to 750 F., reducing said body by forming to about from 40 to of starting cross-section while maintaining said. body within a temperature range not greater than and not substantially below aboutfrom 700 to 750 F., then furthersoaking the body at about from 700 to 750 F. to fully anneal it, then further reducing the resulting alloy material by cold working at least down to 16% of starting cross-section, and then fully annealing the alloy material as so reduced whereby the resulting fully annealed material has strengths favorably comparable with those of presenty known fully annealed wrought aluminum alloys.

4. A method for making a wrought aluminum alloy material comprising soaking a body of metal comprising magnesium 5 to 8%, titanium .10 to 25%, manganese .10 to .25%, boron .001 to .05%, beryllium .0005 to .05 impurities not more than 50%, balance aluminum, for a period of from 15 minutes to 40 hours at a temperature of about from 700 to 750 F., reducing said body by forming to about from 40 to 60% of starting cross-section while maintaining said body within a temperature range not greater than and not substantially below about from 700 to 750 F., then further soaking the body at about from 700 to 750 F. to fully anneal it, then further reducing the resulting alloy material by cold working at least down to 16% of starting cross-section, and then fully annealing the alloy material as so reduced whereby the resulting fully annealed material has strengths favorably comparable with those of presently known fully annealed wrought aluminum alloys.

5. A wrought aluminum alloy material comprising a body of metal comprising magnesium 5 to 8%, titanium .10 to .25%, manganese -.l0 to .25%, beryllium .0005 to .05 impurities not more than 50%, balance aluminum, said body being in a state resulting from soaking for a period of hours at about from 700 to 750 F, and then reduction by forming to about from 40 to 60% of starting cross-section while being maintained within a temperature range not greater than and not substantially below about from 700 to 750 F., and finally full annealing at about from 700 to 750 F., said body being characterized by being further reducible by cold working at least down to 16% of starting cross-section whereupon its ultimate tensile strength is in the vicinity of 75,000 pounds per square inch and its yield strength is in the vicinity of 60,000 pounds per square inch.

6. A wrought aluminum alloy material comprising a body of metal comprising magnesium 5 to 8%, titanium .10 to .25%, manganese .10 to .25%, boron .001 to 05%, beryllium .0005 to .05 impurities not more than 50%, balance aluminum, said body being in a state resulting from soaking for a period of hours at about from 700 to 750 F., and then reduction by forming to about from 40 to 60% of starting cross-section while being maintained within a temperature range not greater than and not substantially below about from 700 to 750 F., and finally full annealing at about from 700 to 750 F., said body being characterized by being further reducible by cold working at least down to 16% of starting cross-section whereupon its ultimate tensile strength is in the vicinity of 75,000 pounds per square inch and its yield strength is in the vicinity of 60,000 pounds per square inch.

7. A wrought aluminum alloy material comprising a body of metal comprising magnesium 5 to 8%, titanium .10 to .25 manganese .10 to .25 beryllium .0005 to .05 impurities not more than .50%, balance aluminum, said body being in a state resulting from soaking for a period of hours at about from 700 to 750 F., and then reduction by forming to about from to 60% of starting cross-section while being maintained within a temperature range not greater than and not substantially below about from 700 to 750 F., then full annealing at about from 700 to 750 F, then further reduction by cold working at least down to 16% of starting cross-section, and then full annealing at about from 700 to 750 B, said body being characterized by an ultimate tensile strength in the vicinity of 50,000 pounds per square inch and a yield strength in the vicinity of 26,000 pounds per square inch.

8. A wrought aluminum alloy material comprising a body of metal comprising magnesium 5 to 8%, titanium .10 to .25%, manganese .10 to .25%, boron .001 to 05%, beryllium .0005 to .05 impurities not more than balance aluminum, said body being in a state resulting from soaking for a period of hours at about from 700 to 750 F., and then reduction by forming to about from 40 to of starting cross-section while being main tained within a temperature range not greater than and not substantially below about from 700 to 750 F., then full annealing at about from 700 to 750 F., then further reduction by cold working at least down to 16% of starting cross-section, and then full annealing at about from 700 to 750 F., said body being characterized by an ultimate tensile strength in the vicinity of 50,000 pounds per square inch and a yield strength in the vicinity of 26,000 pounds per square inch.

References Cited in the file of this patent Transactions of the A. S. M., vol. 44, 1952. (Pages 336 through 347, page 338 especially relied upon.)

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 2,841,512 July 1, 1958 Hugh 8., Cooper It is hereby certified that error appears in the printed specificatioz of the' abo numbered patent requiring correction and that the said Letters Patent ShGu-ifl. read as carrec'hed below.

Column 3, line 61, and column 4, lines 35 and 54;, for "25%", each. occurrence, read -.25%#

Signed and sealed this 7th day of October 1958,

(SEAL) Attest:

KARL AXLINE ROBERT c. WATSON Attesting Ofiicer Commissioner of Patents 

1. A METHOD FOR MAKING A WROUGHT ALUMINUM ALLOY MATERIAL COMPRISING SOAKING A BODY OF METAL COMPRISING MAGNESIUM 5 TO 8%, TITANIUM .10 TO .25%, MANGANESE .10 TO .25%, BERYLLIUM .0005 TO .05%, IMPURITIES NOT MORE THAN .50%, BALANCE ALUMINUM, FOR A PERIOD OF FROM 15 MINUTES TO 40 HOURS AT A TEMPERATURE OF ABOUT FROM 700 TO 750*F., REDUCING SAID BODY BY FORMING TO ABOUT FROM 40 TO 60% OF STARTING CROSS-SECTION WHILE MAINTAINING SAID BODY WITHIN A TEMPERATURE RANGE NOT GREATER THAN AND NOT SUBSTANTIALLY BELOW ABOUT FROM 700 TO 750*F. AND THEN FURTHER SOAKING THE BODY AT ABOUT FROM 700 TO 750*F. TO FULLY ANNEAL IT WHEREBY THE RESULTING ALLOY MATERIAL IS GREATLY FURTHER REDUCIBLE BY COLD WORKING AND IS CAPABLE OF ACHIEVING THEREBY STRENGTHS COMPARABLE WITH THOSE OF PRESENTLY KNOWN HEAT-TREATABLE RESISTANCE FOR SUPERIOR TO THAT OF PRESENTLY ING CORROSION RESISTANCE FAR SUPERIOR TO THAT OF PRESENTLY KNOWN HEAT-TREATABLE WROUGHT ALUMINUM ALLOYS. 